1. Field of the Invention
This invention relates to power skinning knives for removing the hide of slaughtered animals. More specifically, this invention relates to a pneumatically powered skinning knife of the type including a pair of cutting disks driven in opposed cutting oscillations.
2. Description of related art
Power skinning knives employing a pair of oscillating cutting disks are well-known in the art. A modern design includes a pair of adjacent cutting disks, each cutting disk having a plurality of cutting teeth on its circumference. The disks are driven in their opposed cutting oscillations by a pair of pushrods connected to an eccentric drive mechanism operated by a pneumatic motor mounted in the handle of the tool.
Power skinning knives according to this design are described in U.S. Pat. Nos. 4,368,560 and 3,435,522. A similar design is seen in U.S. Pat. No. 2,751,680.
Due to the environment in which these knives are operated and the function which they perform, the gearing and drive mechanism frequently become contaminated with dirt, blood, grease, hair, etc., requiring regular cleaning.
The earliest tools of this type had a very poor seal between the drive mechanism and the cutting mechanism, which allowed frequent contamination of the gears and pushrods of the drive mechanism. The tools were also difficult to open for cleaning, and once open, the drive mechanism could not easily be removed for a thorough cleaning, requiring that the mechanism be cleaned in place. Subsequent designs were somewhat easier to disassemble for cleaning, but still provided inadequate sealing between the cutting and driving mechanisms.
More modern knives such as that shown in U.S. Pat. No. 4,368,560 have been designed with a barrier plate separating the drive mechanism from the cutting disks. Furthermore, a removable cover has been provided to gain access to the drive mechanism for regular cleaning in place. These changes significantly reduced contamination. However, the barrier plate design, while improving the seal between the cutters and the gears, made it impossible to remove the drive mechanism without complete removal of the motor from the housing. Such removal requires special tools which discourages regular maintenance and thorough cleaning.
Moreover, the design of the tool is such that removing the motor from the housing produces wear in the internal pneumatic passageways of the tool causing a loss of pneumatic efficiency each time the unit is disassembled.
A further disadvantage of prior art designs is that the barrier plate separating the cutting disks from the drive mechanism is designed as an integral part of the handle. Because the barrier plate also serves as a bearing surface which is in contact with one of the cutting disks, it needs to be sufficiently hard to avoid premature wear. It would be preferable to make it of steel rather than of the lightweight aluminum typically used for the handle. However, the one piece design means that the bearing surface is made of the same material as the handle, and thus it must be treated with a hardening process to give it the necessary wear-resistance.
Another disadvantage of prior art designs is the high noise level and vibration encountered during use. Still another disadvantage of prior art designs is that a failed main drive bearing often destroyed the housing for the tool requiring the replacement of both the housing and the main drive bearing.
Accordingly, it is an object of the present invention to provide a power skinning knife with a member separating the cutting and driving mechanisms in which the drive mechanism is easily accessible for cleaning through a removable drive mechanism cover and wherein the drive mechanism is removable without the necessity of removing the motor.
A further object of the invention is to provide a skinning knife in which the portion of the tool against which the cutting disks bear can be made of a different material than the handle, permitting the selection of a harder and more wear-resistant material for this portion of the knife.
Another object of the present invention is to provide a skinning knife in which the motor operates with high pneumatic efficiency and in which removal of the motor and disassembly of the tool does not degrade subsequent performance of the tool.
Still another object of the invention is to provide a motor design which may be easily disassembled by hand for cleaning and repair. A further object of the invention is to provide a power skinning knife which produces less noise and vibration than prior art designs.
Yet another object of the invention is to provide a removable main drive bearing mounting member which may be replaced if damaged due to the failure of the main drive bearing.